Bi-directional magnetic fluid clutch



9 v. J. WATTENBERGER 2,616,539

BI-DIRECTIONAL MAGNETIC FLUID CLUTCH Filed Dec. 30, 1949 I n ve n cor:\lehnon J .Watt en ber ger",

His Attorney.

Patented Nov. 4, 1952 BI-DIRECTIONAL MAGNETIC FLUID CLUTCH Vernon J.Wattenberger, Schenectady, N. Y., as- -signorto General ElectricCompany,a corporation of New-York Application December 30, 1949, SerialNo. 135',9.5.5

1 Claim.

This invention re a es "to fluid clut hes and, in particular, to amagnetic type of fluid clutch in which the torque or speed in the outputshaft can be made to go from a maximum value in one directionthrouglrzero to a maximum value in the opposite direction while theinput shaft unidirectionally rotates at a uniform speed.

More specifically, this invention is a clutch comprising a planetary earsystem and a liquid containing a suspended ferrous material.

Magnetic fluid clutches are becoming ever more important in themechanical art, since it is possible by varying a field current of asmall value to regulate the speed and torque of an output shaft producinmany times more power than that used to control it.

The extent of the use of magnetic fluid clutches is so vast that it isdiflicult atthis time to define the scope of their use.

It is an object of this invention to provide an improved fluid magneticclutch.

It is a still further object of this invention to provide a fluidmagnetic clutch having a unidirectional input shaft and a bi-directionaloutput shaft, the torque and speed of which can be changed from amaximum in one direction through zero to a maximum in the otherdirection.

Broadly, this invention comprises a fluid magnetic clutch having twomagnetic coils, one being positioned on either side of a fiat metallicplate connectedto the output shaft. By, varying the current in thesemagnetic coils, the direction and torque of the output shaft iscontrolled.

These and other objects and advantages of this invention will becomeapparent and the invention will be more clearly understood from thefollowing description referring to the accompanying drawing and thefeatures of novelty which characterize this invention Will be pointedout with particularity in the claim annexed to and forming a part ofthis specification.

In the drawing, the single figure is a front view, partly in section, ofthe improved magnetic fluid clutch.

In the drawing, a magnetic fluid clutch l is shown mounted on a baseplate 2. An input shaft 9, connected to some source of power (not shown)extends through a bearing 4 intoa housing 5 for magnetic clutch l. End 6of shaft 3 is adapted to support a coil case 1 in which a coil 8 islocated. Coil 8 comprises a plurality of turns of an insulated conductorwhich produces a magnetic field when energized. Coil case I is securedto end 6 of shaft 3 by some means such as a key.

.ns e ve .9 sur ounds co l case '1 and is s cured thereto. S,le,eve. 9extends axially from'base plate '2 to a ring gear l0 which is securedjtoits opposite end.

A plurality of spider gears II are rotatable about shafts i la which arefixed in cover 5a of housing5. A sun gear 42 is in engagement withspider gears 1| I, while the spider gears, in turn, are in engagementwith ring gear IO. Consequently, .as ring gear l0 turns in onedirection, sun gear 12 turns in the opposite direction. ,Sun gear I2 issecured to a spacer 13 which, ,in turn, is secured to a second coil caseII in which a coil I5 is located. Coil I5 is similar to coil 18.

A circular plate 16, having anexternal diameter slightly larger thanthat of the coil cases '1 and I4, is suspended substantially midwaybetween the two coil cases. Plate I6, in turn, is

secured to an output shaft .11 which is rotatable within a bearing [8and a bushing l9, Bushing I9 is secured to sun gear I2; consequently,the combination of bushing l9, sun gear 12, spacer l3, and coil case Mis revolvable as a unit about output shaft 1]. A bearing guides theupper end or output shaft l1, while collar 2| acts as a seal for theshaft and as a thrust bearing to properly locate plate 16 between thetwo coil cases.

A pair of slip rings 22 are secured to bushing J9. The slip rings are inengagement with brushes 23., which are secured bybrush'holders 24contained in a collar 25 secured to cover 5a.

A pair of channels 26 are drilled or otherwise formed through thecombination of bushing [9, ring .gear [2, spacer l3, and .0011 housingH} to accommodate conductors 21 that connect slip rings ,22 with coill5. 1

With this arrangement, current can .be sent from external conductors 28through the brushes 23 and slip rings 22 to coil IS.

A second set of slip rings 29 are secured to a collar 30 that isfastened to and rotates with coil case 1. Channels 3| carry conductors32 that connect slip rings 29 with coil 8. A pair of brushes 33 aresecured by brush holders 34 which are contained in base plate 2.

This second arrangement provides a current path from external conductors35 to coil 8.

The combination of sleeve 9, coil case I, and end 6 of shaft 3 providesa well for a quantity of oil 36 in which there is suspended ferrousmaterial (not shown). The level of the oil mixture is maintained to apoint somewhere along the sides of coil case M. The level of the oil isnot important to this invention, so long as there is no air gap betweeneither coil case I4 or coil case 1 and plate IS.

The operating theory of this invention is assumed to be that magneticflux lines produced by either coil pass through the oil iron mixtureseparating that coil from plate IS. The magnetic flux, while it passesthrough the oil mixture between the energized coil and plate l8, has noeffect on the oil mixture between the opposite coil and plate 6, sinceplate 16 provides a flux path back to the coil case around the energizedcoil and prevents magnetic fiux from completely passing through theplate.

With this operating theory, if coil 8 is energized, it sets up magneticlines of force which flow through coil case 7 and the oil iron mixtureto plate l6 and then back again to the coil case. The magnetic lines offorce passing through the iron oil mixture align the iron particleswhich, by analogy, causes the oil mixture to freeze; that is,substantially there is a solid between coil case I and plate l6 insteadof the fluid that existed before a current was set up in coil 8.

The torque output and speed of output shaft I1 is directly proportionalto the amount of current set up in coil 8, while the amount of slipbetween output shaft H and input shaft I is inversely proportional tothe amount of current set up in coil 8. This condition exists until thesaturation current is set up in coil 8. The saturation current of coil 8limits the minimum slip and the maximum torque of the output shaft andnaturally any further increase in current in coil 8 will not produce anyincrease in torque or decrease in slip in the output shaft.

In accordance with the previous description, sun gear I2 and,consequently, coil case M, rotate in a direction opposite to that ofinput shaft 3 and coil case I. If coil B is de-energized and currentsupplied to coil 15, flux lines are set up in coil case 14 that passthrough the oil iron mixture on top of plate I 6, then through plate l6and back through the oil iron mixture to coil case I4 again. Once again,magnetic lines of force align the oil iron mixture, but this time themixture on top of plate l6 freezes and the plate is caused to rotate inthe same direction as coil case N. If both coils are simultaneouslyenergized, however, the output torque is a func' tion of the differencebetween the two exciting currents and the direction of the output shaftis determined by the maximum current.

It is interesting to note that if coil 8 is energized while input shaft3 is rotating, a very high polish is imposed upon the bottom surface ofplate l6. Because of this, it is assumed that a frictional drive existsbetween the frozen fluid and plate l8.

Modifications of this invention will occur to those skilled in the artand it is desired to be understood, therefore, that this invention isnot to be limited to the particular arrangement disclosed, but that theappended claim is meant to cover all modifications which are within thespirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

In a magnetic fluid clutch having a unidirectional input shaft and abi-directional output shaft axially aligned therewith, a cup shapedmember secured at its base to the end of said input shaft, a first coilsupported by and rotatable with said input shaft and cup, meansincluding brushes and slip rings for energizin said first coil, a secondcoil axially displaced from said first coil within said cup, means forsupporting said second coil for rotation about said output shaft, meansincluding brushes and slip ring for energizing said second coil, meansincluding a reversing gear system mechanically interconnecting the cupon said input shaft and said supporting means for said second coil andresponsive to rotation of said input shaft for revolving said secondcoil and support in a direction opposite to that of said input shaft andcup, a metal driven plate rigidly secured to the end of said outputshaft and axially interpositioned in said cup between said two coils, amagnetic liquid substantially filling the spaces between each of saidcoils and said driven plate within the cup, and means for electricallyenergizing either or both of said coils while said input shaft isrotating whereby said magnetic fluid is solidified and said output shaftis rotated in the same direction as the coil supplying the higher fluxdensity, the output torque being a function of the difference betweenthe exciting currents in the two coils.

VERNON J \IVATTENBERGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,781,192 Procunier Nov. 11, 19301,796,352 Watson Mar. 17, 1931 1,866,675 Sarazin July 12, 1932 2,453,957Allen Nov. 16, 1948 2,524,150 Vincent Oct. 3, 1950 OTHER REFERENCESBureau of Standards publication, Technical Report 1213, Characteristicsof Some Magnetic- Fluid Clutch Servomechanisms.

